I think that the link jimlynch posted covers the basics pretty well. One thing that I've found is how heavily biased website traffic generally is towards just a few pages out of many. I wouldn't be surprised if you find 90% of your website traffic is driven by 10% of your pages. A web content audit can be very useful for making your site less bloated and more accessible to visitors. Don't be shy about using the tools available to you to inventory and audit the content. Google analytics is your friend, as is a spreadsheet to capture information. At the end of the audit, you will, perhaps for the first time, really understand the entire extent of the site content you are managing. Just make sure that you start out with the scope of the project clearly defined so that you and other understand exactly what you hope to accomplish.

"If you have a website that’s been around for a few years and you’re looking for ways to make some improvements, one of the tactics I recommend is doing a content audit.

When you do a content audit you have a few goals in mind:

Get rid of any low quality or unimportant pagesLook for pages or sections that can be improved or updatedImprove your rankings by more effectively using your link equity, internal anchor text, and interlinking your content"